The present invention relates to apparatus and methods for fractionating living cells according to specific physical characteristics. More particularly the present invention relates to a flowcell fractionator apparatus for obtaining from human semen enriched quantities of male and female sperm in physically separate fractions utilizing the hydrodynamic behavior of sperm in laminar flow.
Both the total number of sperm in an ejaculate and the percentage of sperm thereof which are motile, i.e. capable of progressive swimming movements, can be used as measures of the fertility of the sample, i.e. the liklihood that the sample will achieve fertilization. The motility of sperm has been observed since the earliest use of the microscope of Leeuwenhoek. The variety of techniques which have been developed to assess sperm motility have been summarized by R. W. Atherton in an article entitled "Evaluation of Sperm Motility" published in Techniques of Human Andrology, edited by E. S. E. Hafez, Chapter 7, pages 173-187, Elsevier/North-Holland Biomedical Press, 1977. On pages 181-182 of that article there is described a combination flowcell and spectrophotometer specially adapted for analyzing sperm motility based on orienting sperm in a flowing liquid, and then evaluating their return to randomness. While sperm motility analysis provides valuable information for determining fertility, it does not generally provide physically isolated enriched quantities of male and female fractions useable for artificial insemination.
U.S. Pat. No. 4,007,087 of Ericsson discloses a method of isolating a sperm fraction having a substantially enriched content of male (Y chromosome bearing) sperm. A special albumin solution is placed in a pipette and the albumin is overlaid with sperm. Male sperm swim to the bottom of the solution and the remainder can be culled off.
It would be desirable to provide a simpler, more effective way of obtaining enriched quantities of male and female sperm in physically separate fractions, and to ensure that the sperm in such fractions are motile and viable. It could be used to reduce the incidence of unsuccessful artificial inseminations of domestic animals, e.g. mares and cows. It could also be used to increase a man's natural fertility and to boost a couple's chances of having a boy.